Firebrick and method of making same



, E. H. VAN SCHOICK FIREBRICK AND METHOD 0F MAKING SAME Filed March l5, 1939 Oct. 29, 1940.

Patented Oct. 29, 1940 UNITED sTATEs 2,219,606 Flanmox AND METHOD oF MAKING SAME Elmer l-l. Van Schoick,

Ottawa, Ill., assgnor to Chicago Retort & Fire Brick Company, Chicago, Ill., a corporation of Illinois Application March 139 1939, Serial No. 261,467

9 Claims.

My invention relates to re brick and to the method of making the same, and is more particularly concerned with brick of the stiff mud procexists across each brick which is reflected after a period of service by very definite changes in the brick and these vchanges have long been recognized as a major cause of failure in refractories.

Primarily, spalling is due to the changes which occur in the directly heated'layer of brick.

It has been ascertained that a new clay brick furnace wall has a relatively high degree of initial resistance to thermal spalling, but this resistance is not maintained throughout the life of the refractory. Generally speaking, the lossgin resistance to spalling is due to the creation of a vitrified layer extending inwardly from the ex the vitried layer, relative to the original volume n of this portion of the brick, which sets up stresses that may be increased by subsequent thermal changes toa point where portions of the vitried layer crack and spall oif. A further factor in spalling is' the contaminating action of slag.

Spalling is a particular problem in bricks made by the stiff mud process because of a condition inherent in the method of manufacture. In this process, the clay is extruded through a tapered die to form a stiff mud column which is then cut transversely to form brick blanks. If standard straights having dimensions of 9" x 4% x 21/2" are to be made from the blanks, the cutting of the column establishes the thickness dimension of the brick with allowance for final compression and shrinkage due to drying and'burnlng, while the cut surfaces, or the cross-section of the co1- umn, form the larger or 9" x 41/2" faces of the brick. Pressure is then applied to the two larger surfaces of the blank thus formed to produce'the finished brick.

Due to the extrusion of the clay through the tapered die, the core4 of the column moves at a faster rate through the die than the outer portions thereof and this action produces characteristic and so-called cw lines which are readily apparent in the nished brick and extend generally lengthwise of the clay column. Generally speaking, these ilow lines form a concentric pattern around the longitudinal axis of the clay column and, accordingly, of the corresponding axis portion in the finished brick which is normal to the large faces thereof. This pattern may be diagrammatically illustrated as a succession of concentric circles, or other shaped enclosures depending upon the shape of the die and its extrusion opening, extending from the column axis to the external surfaces of the column. After the brick has been burned, these flow lines become what might be termed planesof cleavage so. that when laid to form a furnace wall with its 9" x 21/2" face exposed to the heat, it is apparent that the disposition of the flow lines,i. e., generally parallel or located at a slight angle to the exposed face of the brick, favors, when spalling does occur, the crumbling and fallingA away of large portions of the exposed face, thus reducing the working thickness of the brick.

It is therefore, the principal object of my invention to devise a re brick 'which materially reduces the aforesaid spalling loss, although made from a clay column extruded by the stiif mud process, and to a method of manufacturing this 25 brick.

'Ihese and further objects of my invention will be set forth in the following specification, reference being had to the accompanying drawing, and the novel means by which said objects are effec- 30 tuated, will be definitely pointed out in the claims.

In the drawing:

Figure 1 is a diagrammatic, elevational view of a typical brick-blank forming machine, as com-` monly used in the manufacture of bricks made by 35 the stiff mud process.

Figure 2 is a'perspective View of a typical fire brick made by the stiff mud process and lshowing the relation of the flow lines to the larger faces thereof. 40

Fig. 3 is a perspective View of a brick similar to that l'shown in Fig. 2, after the brick has undergone a priod of servicein an industrial furnace and showing the characteristic spalling due to the relation of the flow lines in the brick to the ex- .45v

posed face thereof.

Fig. 4 is a perspective view of a brick blank, as severed from the clay column illustrated in Fig. 1, and showing the characteristic flow line pattern around that axis ofthe blank which coincided 50 with the longitudinal axis of the column.

Fig. 5 is a perspective view of a brick formed by applying pressure to the top and bottom surfaces of the blank illustrated in Fig. 4, and showing the flattened and generally deformed appearance 55 which the iiow line pattern presents in the finished brick, particularly with reference to the exposed surface thereof.

For convenience, the invention will be described in connection with the manufacture of a standard straightV re brick having dimensions of 9" x 41/2" x 2%", although it will be understood that the invention is capable of application to the manufacture of re brick having different dimensions.

Referring to Fig. 1 of the drawing, the numeral I0 designates a typical brick-blank forming machine which is loaded with the desired type of re clay that is extruded by means of an auger or screw II through a tapered die I2 to form a clay column I3 that is ordinarily deposited on an endless conveyor and moved away from the die at a rate equal to its speed of. extrusion. After the column has moved a convenient distance from the die, it is periodically cut by a. plurality of spaced wires in the usual manner to form a plurality of brick blanks I4. For purpose of illustration, it will be assumed that the thickness of the column I3, as viewed in Fig. 1, corresponds to the 41/2 inch dimension of the finished brick and that the spacing of the cutting wires is such as will provide the desired thickness of 21/2 inches in the nished brick.

For reasons already noted, this manner of producing the clay column creates flow lines which extend longitudinally thereof and, therefore, generally normal to the wire cut surfaces of the blank I4. In the present manufacture of fire. brick from this type of column, each blank I4 is rested on one of its larger surfaces, i. e., rotated through an angle of ninety degrees from the position illustrated in Fig. 1, -and the blank is then compressed between its large faces, or in a direction generally parallel to that axis of the blank which originally coincided with the longitudinal axis of the column.

The re brick thus produced is illustrated in Fig. 2 and it will be particularly noted that Athe ow lines, indicated by the numeral I5, are generally parallel to the 9 x 21/2" face I Ii of the brick which ordinarily constitutes the exposed face ,of the brick in furnace operations.

In Fig. 3 is illustrated the brick shown in Fig. 2 after it has undergone a period of duty in a furnace and the numeral Il indicates generally the roughened surface of the brick occasioned by spalling of the exposed face I6 and which occurs generally along the flow lines I5.

I have ascertained that it is possible to make re brick by the stiff mud process and to take would otherwise fall completely away from the brick, or be readily loosened during the operation ofY lancing, or by the insertion of other types of bars in the furnace, will remain in place and may in fact, due to the displacement of the flow-line pattern, as hereinafter described, be substantially interlocked with other portions of the brick. The

integrityof the exposed face of the brick is therefore lmaintained for a considerably longer time than is possible with the brick construction illustrated in Fig. 2.

In making my improved brick, each brick blank 7 I4.is compressed between its top and bottom surfaces, as viewed in Fig. 1, and as diagrammatially illustrated in perspective in Fig. 4, that is, pressure is applied to aV pair of the opposite faces of the brick normal to that axis of the brick which coincided with the longitudinal axis of the clay column` I3. 'Ihis method does not require a change in position of the brick, as is necessary in the making of the brick illustrated in Fig. 2, and the final results of the compression are illustrated in the brick shown in 'Fig. 5. The 9" x 41/2 face I8 of the brick blank shown in Fig. 'i1 has been compressed to form the 9" x 21/2" exposed face I9 in which the flow line pattern has been generally compressed and deformed to the extent diagrammatically illustrated "in Fig. 5. The original 9" X21/g" and 2l/2 X41/2 faces of the blank are transformedby the compression into the 9 x 41/2 and 41/2" x 21/2 faces,

being unchanged by the compression.

'It will be particularly noted that the ow lines in this brick are normal to and extend from the exposed face of the brick into the body thereof. Accordingly, if cracking of this face does occur when exposed to the usual temperatures, it will generally progress along the planes of cleavage established by the flow lines, as in the type of brick illustrated in Fig. 2, but due to the flow line relation to the exposed face, the cracked pieces' are more likely to rest in their riginal positions than is possible with the brick shown in Fig. v2 where the ow lines are parallel to the exposed face.

Moreover, the compressing of the brick blank in Fig. 4 not only 4ilattens the 'flow line pattern, but effects some deformation thereof and a lateral flow of the mud which results in an interlocking of fragments of the brick along the ow lines respectively, of the brick, the length of the blank in the heated layer of the brick and this condition also acts to reduce the spalling loss.

The advantages of my improved brick can be better understood by a comparison of the results obtained in a panel spalling test of the bricks illustrated in Figs. 2 and 5. This test was developed by the American Refractories Institute as a means of determining the spalling behavior of fire brick in service and the test has been adopted by the American Society of Testing Materials.

Briefly, the principle of this spalling method is to test a section of a furnace wall rather than individual bricks and in carrying out the method,

fourteen bricks are formed in a Wall panel, corresponding to a section of the Wall of an lndustrial furnace, the panel being eighteen inches.

square and each brick having its 97x 21/2"'face exposed for treatment. This panel' surface is then heated to 1600 C. 2912 F.) for a period of twenty-four hoursand the back of the panel is insulated to maintain a temperature of about 1250 C. on the cool side of the brick. The object of this preheating is to develop in the brick those changes which occur after longer periods of operation at the lower temperatures encountered in industrial practice and, in particular, a. vitried layer along the heated face of the brick that generally corresponds to the layer produced under.4

actual working conditions.

Having thus conditioned the panel, it is then tested for thermalspalling by heating to a temperature of 1400 C. (25525 F.) for a period of ten minutes and then rapidly cooling for ten minutes by exposing the panel to an-air water blast, after which the panel is again heated for a period of ten minutes and this alternate heating and cooling is continued for -twelve complete cycles, each cycle requiring twenty minutes.

The panel is then dismantled and from each brick is removed those-pieces that separate easily, but no attempt is made to remove pieces that require prying or tapping. The percentage loss in weight as determined by this test indicates the spalling resistance of the brickfor a given class of service.

The type of iire brick illustrated in Fig. 2, whenl subjected to the foregoing test, lhas shown as much as a twenty per cen't loss in weight from spalling, as compared to a loss of ve per cent or less for the brick illustrated in Fig. 5.

It has been ascertained that due to the relation of the now lines to the exposed face of my improved brick, the latter is characterized by an increased resistance to abrasion, whether of a solid, liquid, or gaseous nature. When the exposed faces of the nre bricks illustrated in Figs. 2 and 5 are held against a grinding wheel, it has been determined vthat the grinding of the face in the Fig. 2 type of brick can be accomplished with considerably moreease than in the Fig. 5 type ofy brick,l and this condition is believed to be due to what might be termed the grain" ofthe respective bricks as established by their flow lines. In the Fig. 5 type of brick, for example, the pressure of the grinding wheel is across the grain as compared to the grinding with the grain in the Fig. 2 type of brick. I

The practice of my invention is not restricted to disposing the ow .lines normal to the 9" x 2%" face of a standard straight, since these lines may be similarly related to the end or 41/2'" x 21/2" face of the same type of brick, or to any comparable faces of other style of brick. For example, in

straights intended for header courses, the mud column could be extruded through a die measuring {l1/2" x 21/2", cut off at intervals of 9 inches, and then compressed between its 9" x 21/2 faces to a thickness of 21/2 inches and a width of 41/2 inches.

A further method of making the bricks and still accomplishing a disposition of the ow line pattern normal to the exposed face of the brick can be secured in the case of a brick having a 9" x 21/2 exposed face by extruding the clay through a die having similar dimensions. In this case, then, the ow lines, as before, will extend generally parallel to the longitudinal axis of the extruded clay column, but due to the manner of extrusion, the ilow lines are already normal to a transverse plane through the column. Accordingly, when this column is cut at 41/2" intervals to form a brick length, it is simply necessary to compress this blank between its 9" x 2l/2" faces. This method, however, does not secure a deformation of the ow line pattern, as illustrated in Fig. 5. A brick of this character can be employed for stretcher courses in the same manner as the bricks illustrated in Fig. 5.

In the case of header courses, that is, where the exposed faces of the brick are constituted by the 41/2" x 21/2" face, the brick may be formed by eX- truding the clay column through a forming die having similar dimensions and then cuttingthe column at 9" intervals. V`'I'his brick then would be compressed between its 41/2" x 21/2" faces to fully form the brick for burning.

I claim:

1. 'I'he method of making stii mud, fire brickwhich comprises extruding under pressure a stiff mud column through the tapered discharge `opening of a brick machine, the extrusion creating ow lines extending throughout the length of and generally parallel to the longitudinal axis of the 4method defined in claim 3.

column, severing the column transverse to the axis to form a brick blank in which the ow lines are normal to the severed faces, and then compressing the blank between a pair of its opposite faces other than the severed faces sufficient toy cause a pronounced lateral now of the mud composing the blank and a substantial decrease in the dimension of the blank in thev direction of the applied pressure and thereby provide a brick in which a deformed severed face constitutes the face of the brick which is exposed to the heat, the

I ilow lines being normal to the exposed face and the compression and lateral ilow tending to create interlocking pieces of the brick in that llayer of the exposed face which becomes vtriyed during service. j

2. The method of making stiff mud, r brick which comprises extruding under pressure a stiff mud column through the tapered discharge opening of a brick machine, the extrusion creating ow lines extending throughout the length of and generally parallel to `the longitudinal axis of the column and the column having a rectangular cross section whose area approximates that of one of the largest faces of the brick, severing the column transverse to the axis to from a brick blank in which the ow lines are normal to the severed faces, and then compressing the blank between a pair of its opposite faces other than the severed faces suicient to cause a pronounced lateral ow of the mud composing the blank and a substantial decrease in the dimension of the blank and of the severed faces' in the direction of the applied pressure while maintaining the other dimension of the severed faces and thereby'provide a brick in which a deformed severed face constitutes the face of the brick which is exposed to the heat, the ilow lines lbeing normal to the exposed face and the compression and lateral ow tending to create interlocking pieces of the brick in that layer of the exposed face which becomes vitried during service. v

3. The method of making stia mud, nre brick which comprises cutting a stiff mud brick blank from a stiff mud column having flow lines extend-` ing throughout the length of and formed by pressure extrusion of the column through the tapered discharge opening of a brick machine, the ow lines extending throughout the body of the blank and generally normal to the cut faces, and then compressing the blank between a pair of its opposite faces other'than the cut faces suflicient to Vcause a pronounced lat-eral flow of the mud com- 4. A fire brick made in accordance with the method dened in claim 1.

5. A re brick made in accordance with the method dened in claim 2,.

6. A iire brick made in accordance with the '7. A re brick of the stiiii` mud process type having flow lines created by pressure extrusion l and becomes vitried during service, the lines 75 forming agrain-like pattern pressure disarranged relative to the original extrusion pattern sulcient to cause a pronounced owof mud along the ow lines and creating interlocking pieces of brick in the vitrified layer which substantially enhances its resistance to spalling and erosion.

8. A standard straight first brick of the still mud p rocess type having owlines created by pressure extrusion through the tapered discharge opening of a brick machine, extending through the body of the brick normal to that 9" x 21/2" face which `is exposed to the heat and becomes vitried in service, the lines forming a grain-like pattern pressure disarranged relative to the original extrusion pattern sufcient to cause a. pronounced ow of the mud along the ow lines and creating interlocking pieces o! brick in the vitrilied layer which materially enhances its resistance to spalling and erosion.

9. A standard straight re brick of the stiff like pattern pressure disarranged relative to the original extrusion pattern sumcient to cause a pronounced ow of the mud along the ilow lines and creating interlocking pieces of brick in the `litriied layer which substantially enhances its resistance to spalling and erosion.

ELMER VAN. SCHOICK. 

